As a player who plays arbitration daily here is my feedback for this mode, and imo a few things should change.
1. Removes drones and replace them with Newly designed Unique enemies
This promotes Warframe/Weapon variety because the average player in arbitration that can go 30mins and above in random queue are running tank warframes with guns like Arca Plasmor. Unique enemies that are already present in game that can be threatening include Nox's, Bursas,etc. Why not add onto that concept by designing a few new ones?
2. Set rewards at 5 waves or 5 minutes
I don't mind running an arbitration mission for an hour, but rewards are lackluster when they are spaced to far in between. Often times I find myself watching the clock, it's a frustrating experience and makes me feel like there is nothing to really do.
Also Permadeath is not a problem imo.